Extrusion die



Aug. 26, 1958 c. F. POETTER ET AL 2,848,737

EXTRUSION DIE Filed July 18, 1952 United States Patent Ofiice 2,848,737Patented Aug. 26, 1958 EXTRUSION DIE Clarence F. Poetter, Boyertown, andJames E. Spohn, Pottstown, Pa.,- assignors to The Firestone Tire RubberCompany, Akron, Ohio, a corporation of Ohio Application July 18, 1952,Serial No. 299,617

1 Claim. (Cl. 18-8) This invention relates to a unique plasticmonofilament and method and equipment for producing same.

Plastic monofilament strands or strips of extruded, oriented plasticizedvinylidene chloride copolymer are described in Stedman U. S. Patent2,354,435. The cross section suggested by this patent for such filamentsis circular, fiat with rounded edges, semi-elliptical or concavo-convex.In certain applications, as in kitchen cleaning aids such as scouringpads, these plastic filaments were unsatisfactory for efiectivecleansing action of pads embodying them, because of the smooth, roundededges of the filaments.

Various metallic strands or filaments have been incorporated intocleaning rods. Such metallic strands have usually been fiat or roundedin cross section, and have depended for abrasive action on the inherentharshness or rigidity of the metal making up such strands. Metallic wirefor various uses has been disclosed in a number of cross sections innumerous U. S. patents, examples being Taylor 414,090, Howell 723,873and Blount 2,146,788. However, pads made of metallic strands have alwayspossessed certain disadvantages inherent in the metal strandsthemselves. Pads made of iron or steel wire rust rapidly and scratchsilverware, china and cooking vessels of aluminum or copper. Pads madeof copper or brass strands tend to discolor aluminum cooking vessels,and also to scratch silverware and china. Metal cleaning pads quicklybecome soggy and difficult to keep clean.

It is an object of the present invention to provide an improvedfilamentary material designed to overcome the deficiencies of the priorart discussed above. It is also an object to provide suitable equipmentand method for producing such improved filamentary material. The aboveand other objects will become apparent in the following description ofthe invention and in the accompanying drawing, in which:

Fig. 1 is a front elevation of an extruding head suitable for productionof filamentary material of the invention;

Fig. 2 is a fragmentary sectional View taken along line 2, 2 of Fig. 1;and

Fig. 3 is a fragmentary perspective view of the improved filamentarymaterial of the invention, shown partially in section.

Referring to the drawing, a die 11 is provided with a multiplicity oforifices 12, 12, arranged in a circular configuration about the axis ofthe die. The die with 16 orifices shown in Fig. 1 is merely typical of adie suit able for small production of the filament of the invention, anddies having more or less orifices may also be utilized. Although asimple die having a single orifice may be employed, especially forexperimental work, a die having even more than 16 orifices presents theadvantage of providing greater production from a given extruder. Forexample, a die having 32, 64, or even more than 100 orifices may beemployed, and the orifices are preferably arranged in one or moreconcentric circles,

or otherwise arranged, substantially uniformly about the axis of thedie.

The outer face of die 11 is provided with a recess 13 around theperiphery thereof. The recess is adapted to mate with a flange 14 of acap 15. The cap is interiorly threaded to secure the die in properposition against an exteriorly threaded extruder head 16 of an otherwiseconventional extruder (the remainder of which is not shown). Th side ofdie 11 opposite to the outer face thereof is provided with an integralconical portion 17 to insure uniform delivery of plastic material fromextrusion chamber 18 of head 16 to the orfiices 12, 12 of the die, andto avoid creation of a pocket or region of relatively stagnant plasticmaterial, which may be subject to decomposition when maintained .at ahigh temperature for any substanital length of time.

In the production of plastic filament of the invention, a crystallinethermoplastic resin, which may contain plasticizer, heat and/or lightstabilizers, coloring pigment and any other conventional compoundingingredient, is introduced into the extruder in the form of a powder,finely granulated solid or blended compounded resin, and is then heatedin the extruder and delivered to the head 16 as a substantially liquid,plastic, homogeneous material. The head 16 is maintained at a suitablycontrolled high temperature by means of a hot fluid jacket (not shown),or by means of electrical resistance heating means (not shown), as willbe understood by those skilled in the art. An example of a preferredcrystalline resin is a vinylidene chloride polymer, including copolymersor terpolymers consisting of 70% or more of vinylidene chloridepolymerized therein. The bestknown commercial example of resins of thistype is known as Saran, which is understood to include eopolymers of toof vinylidene chloride, with correspondingly, 15 to 5% of vinylchloride. The plasticized and otherwise compounded Saran resin issuitably extruded at a temperature well above C. and usually in therange of to C. From the orifices 12, 12 of die 11, the issuingfilamentary material is carried through a water hath (not shown) toquench the hot, plastic filaments. From the water bath the quenchedfilaments pass to suitable stretching means (not shown); a variety ofsuch means are well known to those skilled in the art, and usuallycomprise a series of rolls driven at successively greater speeds ofrotation. The band of the 16 parallel strands of the extruded plasticfilaments is passed around successive rotating rolls and therebygradually stretched to reduce the cross section of each filament to thedesired extent and also to orient the crystalline resinous portions ofthe plastic substance of the filaments. The drawn, oriented filamentsare wound upon suitable spools, bobbins or rolls and shipped to theuser, such as the manufacturer of knitted plastic tubing, subsequentlyconverted by a simple fabricating operation into a scouring pad.

The filament produced as described above is shown in perspective andpartially in cross section in Fig. 3, and is identified by numeral 19.This preferred filament is substantially elliptical in cross section,except that opposite edges 21, 21 are relatively sharp. The ratio ofthickness 22 of the filament to the width thereof (the distance normallymeasured between opposite edges 21, 21) is in the range of /s to /2, andis preferably substantially /3.

Suitable filaments of plasticized and stabilized Saran resin have beenproduced in cross sections of 13 x 30 mils (thousandths of one inch), 8x 20 mils, 7 x 18 mils and 6.5 x 20 mils. The orifice in the die issuitably made substantially 3 to 4 times larger than the cross sectionof the final filament. For example a commercial filament measuring 13mils in thickness and 30 mils in 3 width was produced from a die inwhich the orifice measured 40 x 115 mils. Both the die orifice and thecross section of the filament produced therefrom were elliptical incross section, in the manner illustrated in the drawing. 1 a a a Theunique plastic filaments of the invention, produced as described above,display tensile strengths in the order of 25,000 to 60,000 pounds persquare inch. The 011'- entedfilaments are tough, lustrous and veryresistant to the action of ordinary organic solvents, such as drycleaning solvents, and also to other cleansing liquids, includingordinary soap and water. The filaments are very flexible and tough, andthey possess long flex lives. The filaments are also substantiallynori-splintering and nonporous. The filaments will not imbibe water, andare actually hydrophobic. The filaments are suitably produced in a greatlatitude of colors, ranging from a straw color or other light color,through many bright and deep colors now well known in the plastics arts,to dark colors, and even to black.

As indicated above, a varietyof difierent compounding materials and/orpigments may be incorporated into the resin mixture prior to extrusionof the filaments. As a further example, one or more fluorescent pigmentsor materials are suitably incorporated into the plastic mixture, and theresulting elliptical filament displays a fluorescent color. Dependingupon the particular fluorescent pigment incorporated into the mixture,the resulting filament is luminous in the dark, and/ or visibly glows indaylight or in the presence of ultra-violet light, to make the articlecontaining the filament stand out and attract the attention of casualobservers. Filaments containing an inorganic fluorescent pigment, suchas the activated metal sulfides, are luminous in the dark immediatelyafter exposure to ordinary light or invisible ultraviolet radiation, andare suitably compounded to project a more than 50% of the incidentvisible light of daylight in the dominant wave band. Filamentscontaining certain organic fluorescent pigments, for example asdisclosed in U. S. Patent 2,498,592, project substantially more of thedaylight of a corresponding color in the 4 incident visible light, oftenin of such visible light.

The die 11 is made of a suitable tough, corrosionresistant metal, suchas a number of the stainless steel alloys and other alloys high innickel and/ or chromium. Nickel and alloys high in nickel are especiallysuitable for the material of die 11, since nickel dies have been foundto be especially resistant to corrosion or wearing away when employedfor extrusion of crystalline vinylidene chloride polymers of the typecontemplated herein. Die 11 may also be formed of any suitably hardmetal and plated with nickel and/or chromium to protect the operativesurfaces thereof.

We claim:

A die for production of a plastic filament substantially elliptical incross section and having sharp opthe range of to posite edges, the diecomprising a multiplicity of sub- 7 stantially elliptically shapedorifices of uniform size, the orifices being symmetrically arranged inrespect to the center axis of the die, and the dimensions of saidorifices being substantially 3 to 4 times larger than the correspondingdimensions of said filament, the die being provided with an integralconical structure on the inner face thereof, said structure having acomplete conical surface, the axis of which is coaxial with the centeraxis of the die and the vertex of which is directed away from the outerface of the die, said structure being adapted to distribute plasticmaterial uniformly to each 'ofthe orifices of the die.

References Cited in the fileof this patent UNITED STATES PATENTS UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,848,737August 26, 1958 Clarence Fa Poetter et all,

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

Column 1, line 28, for rods' read m pads column line 9, for "Thread TheSigned and sealed this 21st day of July 1959,

( SEAL) Attest:

KARL AXLINE ROBERT c. WATSON Commissioner of Patents Attesting Oflicer

